John Stewart Bell (1928–1990), a truly deep and serious thinker, was one of the leading physicists of the twentieth century. He became famous for his discovery that quantum mechanics implies that nature is nonlocal, that is, that there are physical influences between events that propagate faster than light.

From 1960 until his death Bell worked at the Conseil Européen pour la Recherche Nucléaire (CERN; European Laboratory for Particle Physics) in Geneva, Switzerland, on the physics of particle accelerators, making a number of important contributions to high-energy physics and quantum field theory. Noteworthy was his discovery in 1969, together with Roman W. Jackiw, of the so-called "Bell-Jackiw-Adler" anomaly (discovered independently by Stephen Adler), a mechanism explaining physical effects such as neutral pion decay (which are unexplainable on the basis of the symmetries of the classical field Lagrangian), in...